1. Field of the Invention
The present invention relates to a sealed cased magnetic switch and, more particularly, to a sealed cased magnetic switch capable of reducing noise of a switching operation.
2. Description of the Related Art
A magnetic switch, a device used for switch a power supply line, is a relatively low voltage electric power switch utilized for extensive purposes including an industrial purpose, a household purpose, electric vehicle purpose, and the like. The magnetic switch is configured to switch a power supply circuit by moving a movable contact connected to a movable core, to a circuit opening position where a movable contactor connected to the movable core is separated from a corresponding fixed electrode, or to a circuit closing position where the movable contactor is brought into contact with the corresponding fixed electrode, by moving the movable core by using magnetic force of a coil magnetized or demagnetized according to supply or interruption of control electric power source. If the contact of the movable contactor at the position where the movable contactor is in contact with the fixed electrode becomes poor due to an external factor such as vibration, an impact, and the like, at the circuit closing position, the contact may be fused, damaged, and the like to possibly cause a more critical electrical incident, so a contact pressure spring is employed to apply elastic force to the position at which the movable contactor is in contact with the corresponding fixed electrode.
However, in the magnetic switch, the use of the contact pressure spring having a high elastic force to obtain the operational reliability during the contact operation increases an impact when the movable contactor is brought into contact with the fixed electrode during the circuit closing operation, causing severe impact noise.
In particular, the magnetic switch used for homes or electric vehicles urgently needs to have a low-noise structure that does not generate such impact noise.
Meanwhile, the related art sealed cased magnetic switch includes one contact pressure spring installed around a driving shaft of a movable contactor, in which one end of the contact pressure spring is supported by a central portion of the movable contactor and the other end of the contact pressure spring is supported by a spring seat fixedly installed on the driving shaft. The related art sealed cased magnetic switch has a structure in which the contact pressure spring and the driving shaft providing a contract driving force are placed at the central portion of the movable contactor, while an outer portion of the movable contactor collides with the fixed electrode during a contact operation. Thus, a large impact is applied to the portion of the movable contactor which is brought into contact with the fixed electrode, and as shown in FIG. 1, as the stroke of the distance along which the movable contactor is moved during the contact operation increases, a total contact pressure has a lengthy nonlinear interval (i.e., the interval in which the total contact pressure is stationary without a variation in FIG. 1) starting from a collision. As the nonlinear interval is lengthy, more severe noise is generated. Thus, in the related art sealed cased magnetic switch, the nonlinear interval is lengthy in terms of the variation characteristics of the total contact pressure as the contact operation of the movable contactor is performed, generating severe noise.